Alright guys...i happen to have THE solution for this.
Watch this video
http://video.google.com/videoplay?docid=-3522676950230105924#
The guy makes this box enclosure for the window.
He cracks the window open a bit, then puts blinds over it.
Then he makes a vent box. Its a rectangular box with some foam lined on the inside...and a hole in it.
From then he puts some "speaker cloth" over it to prevent light leaks and filter the air.
Then he attaches the whole vent box to the wall over the window.
From the outside it appears just like some bamboo blinds in a dark room...nothing suspicious.